The power supply system is the electrical energy that is sent from the power grid to the enterprise and is distributed to various workshops or power units after the voltage is reduced. It consists of high-voltage and low-voltage distribution lines, transformer (distribution) substations and electrical equipment. Generally, large and medium-sized enterprises have total step-down transformer substations, reducing the voltage of 35 to 110 kV to 6 to 10 kV, and supplying power to workshop substations or high-voltage motors and other electrical equipment. The main electrical equipment in a transformer (distribution) substation is a step-down main transformer and power receiving and distribution equipment and devices, including switchgear, busbars, protective appliances, measuring instruments and other electrical equipment. In the process of power transmission and distribution within an enterprise, power loss and power loss occur when current passes through equipment such as lines and transformers. These losses are called power supply losses. The percentage of the lost energy to the input power (or the percentage of the power loss to the input power) is called the line loss rate, or line loss rate for short. In addition, power loss and power loss change with the line length and the type of the conductor, the size of the transformer and the load changes.